The American Cancer Society estimated that in 2004, breast or colorectal cancer would strike over 350,000 Americans and close to 100,000 people would die from these diseases. The National Surgical Adjuvant Breast and Bowel Project(NSABP) is a multi-center clinical cooperative trials group with nearly 200 member institutions located throughout the US, Canada and Puerto Rico. The primary research objective of the NSABP is to conduct therapeutic research designed to improve the survival and the quality of life for persons with breast or colorectal cancer. This goal is achieved through the conduct of definitive phase III trials and the developmental efforts that lead to them. In calendar years 2002 and 2003, the NSABP entered 10,270 breast cancer patients and 962 colorectal cancer patients into adjuvant therapy trials. According to NCI data, this represents 64% of the breast cancer patients and 78% of the colorectal cancer patients entering NCI sponsored phase III cooperative group adjuvant breast or colorectal adjuvant trials. The NSABP integrates key behavior and health outcomes into its phase III trials to provide added value to the traditional endpoints of disease-free and overall survival. The NSABP also conducts correlative laboratory research in conjunction with its clinical trials designed to improve methods of assessing prognosis and predicting response to treatment with the aim of optimizing therapy for individual patients. In the proposed project period our aim will be to continue to improve breast and colorectal cancer therapies through the development and conduct of well-designed Phase III adjuvant therapy trials which will be carried out at our extensive network of affiliated members throughout North America.